The Caliciviridae is a family of positive-strand RNA viruses and consists of five genera designated: (1) Norovirus (with species Norwalk virus);(2) Sapovirus (with species Sapporo virus);(3) Vesivirus (with species, feline calicivirus and vesicular exanthema of swine virus);(4) Lagovirus (with species rabbit hemorrhagic disease virus and European brown hare syndrome virus) and (5) Nebovirus (with species Newbury-2 virus). The Caliciviruses Section in LID is focused on one major goal: lessen the disease burden from caliciviruses that cause disease in humans. Noroviruses are the primary focus of our research because they are the major calicivirus pathogens in humans. Noroviruses are antigenically-diverse and cause the majority of nonbacterial epidemic gastroenteritis outbreaks. They are important agents of sporadic, acute gastroenteritis in infants and young children and can cause life-threatening diarrhea in immunocompromised individuals. Because a major technical challenge in the study of these viruses is the inability to grow viruses in cultured cells, our laboratory has developed calicivirus replication systems and animal models to establish parameters of infection and immunity. We are exploring the efficacy of various norovirus vaccine candidates and developing antibodies with the potential for therapeutic use. The availability of effective control measures for the noroviruses will be an important medical advance in the control of these ubiquitous pathogens.